Subtraction Query

Hello,
I have a database (db)in MS-Access 2003.
The db is being used to manage the deployment &
migration of 500+ laptops.

I have a field named "completed". I would like to
write a query that subtracts the number of completed
laptops from the total number of laptops. I would like
to show results in a chart...

Can someone point me to some samples or examples????

Thank You,

Charles

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